Stabilization of video cameras and other optical devices is a challenge, particularly when these instruments are mounted on moving platforms such as trucks, tanks, aircraft or ships. An optical device mounted on such a platform can be used in a variety of ways including news reporting, industrial reporting or military reconnaissance and intelligence purposes. However, such platforms vibrate when the vehicles to which they are mounted are in operation and optical devices mounted to such platforms require stabilization to compensate for the erratic movement of the vehicle, which can be unpredictable. Vehicle movement and vibration problems become even more serious when the magnification of such instruments is increased; not only is the object being viewed magnified, but the motion thereof relative to the moving platform is also magnified. Therefore, when optical devices are mounted on these vehicles it is critical that the instrument itself be stabilized.
Stabilized optical systems attempt to overcome vibration problems by isolating the optical instrument(s) from angular and linear disturbances. Because these instruments are mounted on moving external platforms, the optics must also be isolated from air loads and weather conditions while the optics of the instrument are inertially stabilized. Optical stabilization systems address these problems in different ways while attempting to provide the angular acceleration, angular rates and angular coverage required to obtain the maximum benefit of advanced optical instruments. In particular, some conventional systems have both coarse and fine adjustment motors to provide a wide range of motion while maintaining a sufficient degree of positional accuracy.
Stabilization systems exist which use a number of different designs and electromechanical components. As an illustration, U.S. Pat. No. 3,638,502 discloses a "stabilized camera mount" which is made pendulous to be self-erecting by relying on the gravitational and inertial forces of the system itself. This stabilized camera mount is not a combination coarse and fine adjustment stabilization system. Instead, the camera mount is stabilized directly by a spinning mass gyro, uses a helical spring with alternating metallic and plastic strips for passive vibration isolation and utilizes rotational motors and gears to move the camera line of sight. Thus, the camera mount relies on a number of complex movements which necessitate the use of a number of gears and motors to achieve stabilization. The system design crowds these components into a relatively small envelope, thereby exposing cables and wires to moving parts and increasing the potential for system malfunction or failure.
Also noteworthy is U.S. Pat. No. 4,752,791, which discloses a general purpose "camera mount" that is driven by an elaborate system of motors and sprockets. Notwithstanding the complexity of the camera mount, the system is a coarse system only and does not provide for fine stabilization of an optical instrument. The camera mount includes an "open rectangular frame" which cannot be rigid while in operation and prevents the camera mount from providing high servo bandwidth and fine stabilization to the optical instrument. Like the '502 patent, the elaborate system of motors and sprockets making up the invention disclosed in the '791 patent increases the potential for system malfunction or failure because of the intricacies of the system and the large number of moving parts and wires mounted within close proximity. In addition, the number of parts and wires each contribute to the cost of the device.
Consequently, there is a need for a system for stabilizing optical instruments that has the wide range and precision capability of separate coarse and fine adjustment systems. However, such a system would preferably also minimize the potential for system malfunction or failure by decreasing the number of moving parts such as rotational drive motors.